CN111020341B - Production process of powder sintered alnico permanent magnetic alloy - Google Patents
Production process of powder sintered alnico permanent magnetic alloy Download PDFInfo
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Abstract
The invention discloses a production process of powder sintered alnico permanent magnetic alloy, which is characterized by comprising the following steps of: step one, weighing materials: weighing 24.5-26% of Co, 13.5-14.5% of Ni, 2-3% of Cu, 8-9% of Al, 0-0.5% of Nb, 0-0.5% of Ti, 0-0.3% of B and 46.2-52% of Fe according to weight percentage; step two, vacuum melting; step three, primary mixing; step four, mixing again; step five, pressing; step six, sintering: sintering the pressed product in a vacuum sintering furnace for 8 grades, and then cooling to obtain a sintered product; step seven, heat treatment; and step eight, tempering. The invention improves the magnetic property, the magnetic property Br of the finished product produced by the invention can reach 1232mT, the Hcb can reach 53.4kA/m, and the BHmax can reach 37.6kJ/m3。
Description
Technical Field
The invention relates to a production process of powder sintered alnico permanent magnetic alloy.
Background
Nowadays, a permanent magnetic material is a very important functional material, and at present, the mainstream permanent magnetic materials used include neodymium iron boron, samarium cobalt, ferrite, alnico, iron chromium cobalt, and the like, and along with the recent rapid development of rare earth permanent magnets, the market share of alnico is gradually reduced, but alnico still occupies a place in some fields with high requirements on temperature property due to its specific physical properties. The alnico permanent magnetic alloy is divided into cast alnico and sintered alnico according to the manufacturing process, and the conventional alnico permanent magnetic alloy is divided into two types, three types, five types, six types, eight types, nine types and the like according to the composition of formula components. The technological process of sintering alnico comprises the steps of pulverizing, mixing, pressing, sintering, heat treatment, grinding, inspection and packaging. The invention discloses a production process for sintering alnico permanent magnetic alloy by using CN01130484.7 powder, which relates to eight production processes, and the formula of the alnico permanent magnetic alloy is as follows: 6 to 8 percent of Ni, 36.1 to 37.9 percent of Co, 2.5 to 5 percent of Cu, 0.5 to 1.5 percent of Nb, 10 to 14 percent of Ni, 5 to 8 percent of Ti and the balance of Fe, which are all in mass percent and do not relate to the production process of sintering AlNiCo. The magnetic performance of the prior sintered AlNiCo five-class material is the mark AlNiCo34/5, the Br thereof is 11200mT, the Hcb thereof is 48kA/m, and the BHmax thereof is 34kJ/m3Compared with the common five types of Br1200mT, Hcb 48kA/m and BHmax 37kJ/m3And the magnetic performance of five types of sintering is not improved for years, and if the formula is adjusted and the process method is improved, the performance level of five types of common casting can be met.
Disclosure of Invention
The invention aims to overcome the defects of the existing product and provides a production process for sintering alnico powder into permanent magnetic alloy.
In order to achieve the purpose, the invention is realized by the following technical scheme:
the production process of the powder sintered alnico permanent magnetic alloy comprises the following steps:
step one, weighing materials: weighing 24.5-26% of Co, 13.5-14.5% of Ni, 2-3% of Cu, 8-9% of Al, 0-0.5% of Nb, 0-0.5% of Ti, 0-0.3% of B and 46.2-52% of Fe according to weight percentage;
step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow;
step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen;
step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three to obtain alloy powder;
step five, pressing: pressing and forming the alloy powder by using a dry powder press to obtain a pressed product;
step six, sintering: sintering the pressed product in a vacuum sintering furnace for 8 grades, and then cooling and discharging to obtain a sintered product;
step seven, heat treatment: preheating a sintered product for a period of time, then putting the preheated sintered product into a high-temperature furnace for solid solution for 20 minutes, wherein the solid solution temperature is 1280 ℃, then cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for a period of time when the temperature is reduced to 900 ℃, and then directly cooling the sintered product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590 and 610 ℃, and the strength of a magnetic field is more than 3000 Gs;
step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours (first-stage tempering); cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours (secondary tempering); cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours (third-stage tempering), and then continuously cooling and discharging to obtain a finished product.
The 8-stage sintering comprises the following steps:
step a), heating to 500 ℃ from room temperature for 1-3 hours;
step b), preserving heat for 2-3 hours at 500 ℃;
step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours;
step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours;
step e), continuously heating to 900-1200 ℃, and then preserving heat for 2-3 hours;
step f), continuously heating to 1200-1360 ℃, and then preserving heat for 2-4 hours;
step g), preserving heat for 2-6 hours at 1360 ℃;
step h), continuously raising the temperature to 1360-1370 ℃, and then preserving the heat for 0.5-1 hour.
In the seventh step, the preheating temperature is 900 ℃.
In step seven, the period of time is 20 minutes.
Some times are 10-20 minutes.
The pressed density is 5.5-6.0 g/cm3。
The invention has the following beneficial effects: according to the invention, the copper content is reduced, so that the coercive force is reduced, the decrease of the coercive force is compensated by adding titanium, the residual magnetism is improved by increasing the contents of cobalt and iron, and meanwhile, the eutectic temperature of the alloy is reduced by adding trace element boron, so that the growth of crystal grains is facilitated, and the sintering density is improved; the method adopts 8-level sintering, the temperature of the last sintering is raised to 1360-1370 ℃, then the temperature is kept for 0.5-1 hour, and crystal grains are further grown by short-time temperature rise, and meanwhile, the product deformation caused by overhigh sintering temperature is avoided; the heat treatment of the invention adopts preheating at 900 ℃ and solid solution at 1280 ℃, then when the temperature is reduced to 900 ℃, the isothermal thermomagnetic treatment is carried out for a certain time, and then the air cooling is carried out directly to the normal temperature, the process effectively reduces the precipitation of the gamma phase, and simultaneously, the 590-610 ℃ isothermal thermomagnetic treatment is adopted to avoid the rapid temperature reduction to cause alpha → alpha 1 + alpha2Insufficient decomposition, thereby improving the magnetic performance; the magnetic performance Br of the finished product produced by the invention can reach 1243mT, Hcb can reach 54.6kA/m, and BHmax can reach 38.5kJ/m3。
Detailed Description
The technical solution of the present invention is further explained below:
example 1:
the production process of the powder sintered alnico permanent magnetic alloy comprises the following steps:
step one, weighing materials: weighing 24.5-26% of Co, 13.5-14.5% of Ni, 2-3% of Cu, 8-9% of Al, 0-0.5% of Nb, 0-0.5% of Ti, 0-0.3% of B and 46.2-52% of Fe according to weight percentage;
step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow;
step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen so as to remove oxidized impurities;
step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three through a V-shaped or three-dimensional mixer to obtain alloy powder;
step five, pressing: pressing the alloy powder with a dry powder press to form a pressed product with a pressing density of 5.5-6.0 g/cm, wherein the die can be square, circular, annular or other shapes3；
Step six, sintering: placing the pressed product into a sintering box by adopting a vacuum sintering furnace, adopting 36-60-mesh corundum as a filler, ensuring that the sand purity Al2O3 is more than 98 percent and the sintering vacuum degree is required to be less than 10Pa, adopting 8-grade sintering in the sintering process, and then cooling and discharging to obtain a sintered product;
step seven, heat treatment: preheating a sintered product at 900 ℃ for 20 minutes, putting the preheated sintered product into a high-temperature furnace for solid solution at 1280 ℃ for 20 minutes, cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for 10-20 minutes when the temperature is reduced to 900 ℃, directly cooling the product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590-610 ℃, and the strength of a magnetic field is greater than 3000 Gs;
the five types of Al-Ni-Co are single-phase solid solution alpha phase at the temperature of more than 1200 ℃, alpha + gamma exists at the temperature of 1200-900 ℃, the gamma phase is a non-magnetic phase, the thermomagnetic treatment is carried out at the temperature of 900-600 ℃ to generate alpha → alpha 1 + alpha 2 amplitude modulation decomposition, and the key for obtaining high magnetic performance is to reduce the generation of the gamma phase. The conventional process adopts preheating at 900 ℃, solid solution at 1280 ℃, heat preservation for 12-18 minutes, air cooling, temperature control cooling in a magnetic field, and the magnetic field cooling time is 12-18 minutes. The conventional process still has a small amount of gamma phase generated in the range of 1200-900 ℃. The method adopts 900 ℃ preheating, 1280 ℃ solid solution, heat preservation for 12-18 minutes, air cooling for rapid 1200-900 ℃, then 590-610 ℃ isothermal thermomagnetic treatment for 10-20 minutes, and air cooling naturally, the process effectively reduces the precipitation of gamma phase, and simultaneously adopts 590-610 ℃ isothermal thermomagnetic treatment to avoid insufficient alpha → alpha 1 + alpha 2 decomposition caused by too rapid temperature reduction.
Step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours (first-stage tempering); cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours (secondary tempering); cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours (third-stage tempering), and then continuously cooling and discharging to obtain a finished product.
The 8-stage sintering comprises the following steps:
step a), heating to 500 ℃ from room temperature for 1-3 hours;
step b), preserving heat for 2-3 hours at 500 ℃;
step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours;
step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours;
step e), continuously heating to 900-1200 ℃, and then preserving heat for 2-3 hours;
step f), continuously heating to 1200-1360 ℃, and then preserving heat for 2-4 hours;
step g), preserving heat for 2-6 hours at 1360 ℃;
step h), continuously raising the temperature to 1360-1370 ℃, and then preserving the heat for 0.5-1 hour.
The invention reduces the copper content to reduce the coercive force, compensates the reduction of the coercive force by adding titanium, increases the cobalt and iron content to improve the remanence, and simultaneously adds the trace element boron to reduce the eutectic temperature of the alloy, thereby being beneficial to the growth of crystal grains and the sintering densityImprovement of (1); the method adopts 8-level sintering, the temperature of the last sintering is raised to 1360-1370 ℃, then the temperature is kept for 0.5-1 hour, and the crystal grains are further grown by short-time temperature rise, and meanwhile, the product deformation caused by overhigh sintering temperature is avoided; the heat treatment of the invention adopts preheating at 900 ℃ and solid solution at 1280 ℃, then when the temperature is reduced to 900 ℃, the isothermal thermomagnetic treatment is carried out for a certain time, and then the air cooling is carried out directly to the normal temperature, the process effectively reduces the precipitation of the gamma phase, and simultaneously, the 590-610 ℃ isothermal thermomagnetic treatment is adopted to avoid the rapid temperature reduction to cause alpha → alpha 1 + alpha2Insufficient decomposition, thereby improving the magnetic performance; the magnetic performance Br of the finished product produced by the invention can reach 1238mT, the Hcb can reach 54.2kA/m, and the BHmax can reach 38.5kJ/m3。
Example 2:
the production process of the powder sintered alnico permanent magnetic alloy comprises the following steps:
step one, weighing materials: weighing 24.8% of Co, 14% of Ni, 2.2% of Cu, 8.3% of Al, 0.3% of Nb, 0.1% of Ti, 0.1% of B and 50% of Fe according to weight percentage;
step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow;
step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen so as to remove oxidized impurities;
step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three through a V-shaped or three-dimensional mixer to obtain alloy powder;
step five, pressing: pressing the alloy powder with a dry powder press to form a pressed product with a pressing density of 5.5-6.0 g/cm, wherein the die can be square, circular, annular or other shapes3；
Step six, sintering: placing the pressed product into a sintering box by adopting a vacuum sintering furnace, adopting 36-60-mesh corundum as a filler, ensuring that the sand purity Al2O3 is more than 98 percent and the sintering vacuum degree is required to be less than 10Pa, adopting 8-grade sintering in the sintering process, and then cooling and discharging to obtain a sintered product;
step seven, heat treatment: preheating a sintered product at 900 ℃ for 20 minutes, putting the preheated sintered product into a high-temperature furnace for solid solution at 1280 ℃ for 20 minutes, cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for 10-20 minutes when the temperature is reduced to 900 ℃, directly cooling the product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590-610 ℃, and the strength of a magnetic field is greater than 3000 Gs;
the five types of Al-Ni-Co are single-phase solid solution alpha phase at the temperature of more than 1200 ℃, alpha + gamma exists at the temperature of 1200-900 ℃, the gamma phase is a non-magnetic phase, the thermomagnetic treatment is carried out at the temperature of 900-600 ℃ to generate alpha → alpha 1 + alpha 2 amplitude modulation decomposition, and the key for obtaining high magnetic performance is to reduce the generation of the gamma phase. The conventional process adopts preheating at 900 ℃, solid solution at 1280 ℃, heat preservation for 12-18 minutes, air cooling, temperature control cooling in a magnetic field, and the magnetic field cooling time is 12-18 minutes. The conventional process still has a small amount of gamma phase generated in the range of 1200-900 ℃. The method adopts 900 ℃ preheating, 1280 ℃ solid solution, heat preservation for 12-18 minutes, air cooling for rapid 1200-900 ℃, then 590-610 ℃ isothermal thermomagnetic treatment for 10-20 minutes, and air cooling naturally, the process effectively reduces the precipitation of gamma phase, and simultaneously adopts 590-610 ℃ isothermal thermomagnetic treatment to avoid insufficient alpha → alpha 1 + alpha 2 decomposition caused by too rapid temperature reduction.
Step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours (first-stage tempering); cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours (secondary tempering); cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours (third-stage tempering), and then continuously cooling and discharging to obtain a finished product.
The 8-stage sintering comprises the following steps:
step a), heating to 500 ℃ from room temperature for 2 hours;
step b), preserving heat for 2 hours at 500 ℃;
step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours;
step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours;
step e), continuously heating to 900-1200 ℃, and then preserving heat for 3 hours;
step f), continuously heating to 1200-1360 ℃, and then preserving heat for 3 hours;
step g), keeping the temperature for 5 hours at 1360 ℃;
step h), continuously raising the temperature to 1360-1370 ℃, and then preserving the temperature for 0.5 hour.
According to the invention, the copper content is reduced, so that the coercive force is reduced, the decrease of the coercive force is compensated by adding titanium, the residual magnetism is improved by increasing the contents of cobalt and iron, and meanwhile, the eutectic temperature of the alloy is reduced by adding trace element boron, so that the growth of crystal grains is facilitated, and the sintering density is improved; the method adopts 8-level sintering, the temperature of the last sintering is raised to 1360-1370 ℃, then the temperature is kept for 0.5-1 hour, and the crystal grains are further grown by short-time temperature rise, and meanwhile, the product deformation caused by overhigh sintering temperature is avoided; the heat treatment of the invention adopts preheating at 900 ℃ and solid solution at 1280 ℃, then when the temperature is reduced to 900 ℃, the isothermal thermomagnetic treatment is carried out for a certain time, and then the air cooling is carried out directly to the normal temperature, the process effectively reduces the precipitation of the gamma phase, and simultaneously, the 590-610 ℃ isothermal thermomagnetic treatment is adopted to avoid the rapid temperature reduction to cause alpha → alpha 1 + alpha2Insufficient decomposition, thereby improving the magnetic performance; the magnetic performance Br of the finished product produced by the invention can reach 1243mT, Hcb can reach 53.2kA/m, BHmax can reach 37.8/m3。
Example 3:
the production process of the powder sintered alnico permanent magnetic alloy comprises the following steps:
step one, weighing materials: weighing 24.5 percent of Co, 13.5 percent of Ni, 2 percent of Cu, 8 percent of Al, 0-0.5 percent of Ti, 0.1 percent of B and 46.2 percent of Fe according to weight percentage;
step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow;
step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen so as to remove oxidized impurities;
step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three through a V-shaped or three-dimensional mixer to obtain alloy powder;
step five, pressing: pressing the alloy powder with a dry powder press to form a pressed product with a pressing density of 5.5-6.0 g/cm, wherein the die can be square, circular, annular or other shapes3；
Step six, sintering: placing the pressed product into a sintering box by adopting a vacuum sintering furnace, adopting 36-60-mesh corundum as a filler, ensuring that the sand purity Al2O3 is more than 98 percent and the sintering vacuum degree is required to be less than 10Pa, adopting 8-grade sintering in the sintering process, and then cooling and discharging to obtain a sintered product;
step seven, heat treatment: preheating a sintered product at 900 ℃ for 20 minutes, putting the preheated sintered product into a high-temperature furnace for solid solution at 1280 ℃ for 20 minutes, cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for 10-20 minutes when the temperature is reduced to 900 ℃, directly cooling the product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590-610 ℃, and the strength of a magnetic field is greater than 3000 Gs;
the five types of Al-Ni-Co are single-phase solid solution alpha phase at the temperature of more than 1200 ℃, alpha + gamma exists at the temperature of 1200-900 ℃, the gamma phase is a non-magnetic phase, the thermomagnetic treatment is carried out at the temperature of 900-600 ℃ to generate alpha → alpha 1 + alpha 2 amplitude modulation decomposition, and the key for obtaining high magnetic performance is to reduce the generation of the gamma phase. The conventional process adopts preheating at 900 ℃, solid solution at 1280 ℃, heat preservation for 12-18 minutes, air cooling, temperature control cooling in a magnetic field, and the magnetic field cooling time is 12-18 minutes. The conventional process still has a small amount of gamma phase generated in the range of 1200-900 ℃. The method adopts 900 ℃ preheating, 1280 ℃ solid solution, heat preservation for 12-18 minutes, air cooling for rapid 1200-900 ℃, then 590-610 ℃ isothermal thermomagnetic treatment for 10-20 minutes, and air cooling naturally, the process effectively reduces the precipitation of gamma phase, and simultaneously adopts 590-610 ℃ isothermal thermomagnetic treatment to avoid insufficient alpha → alpha 1 + alpha 2 decomposition caused by too rapid temperature reduction.
Step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours (first-stage tempering); cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours (secondary tempering); cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours (third-stage tempering), and then continuously cooling and discharging to obtain a finished product.
The 8-stage sintering comprises the following steps:
step a), heating to 500 ℃ from room temperature for 1 hour;
step b), preserving heat for 2 hours at 500 ℃;
step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours;
step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours;
step e), continuously heating to 900-1200 ℃, and then preserving heat for 2 hours;
step f), continuously heating to 1200-1360 ℃, and then preserving heat for 2 hours;
step g), preserving heat for 2-6 hours at 1360 ℃;
step h), continuously raising the temperature to 1360-1370 ℃, and then preserving the heat for 0.5-1 hour.
According to the invention, the copper content is reduced, so that the coercive force is reduced, the decrease of the coercive force is compensated by adding titanium, the residual magnetism is improved by increasing the contents of cobalt and iron, and meanwhile, the eutectic temperature of the alloy is reduced by adding trace element boron, so that the growth of crystal grains is facilitated, and the sintering density is improved; the method adopts 8-level sintering, the temperature of the last sintering is raised to 1360-1370 ℃, then the temperature is kept for 0.5-1 hour, and the crystal grains are further grown by short-time temperature rise, and meanwhile, the product deformation caused by overhigh sintering temperature is avoided; the heat treatment of the invention adopts preheating at 900 ℃ and solid solution at 1280 ℃, then when the temperature is reduced to 900 ℃, the isothermal thermomagnetic treatment is carried out for a certain time, and then the air cooling is carried out directly to the normal temperature, the process effectively reduces the precipitation of the gamma phase, and simultaneously, the 590-610 ℃ isothermal thermomagnetic treatment is adopted to avoid the rapid temperature reduction to cause alpha → alpha 1 + alpha2Insufficient decomposition, thereby improving magnetic propertiesEnergy is saved; the magnetic performance Br of the finished product produced by the invention can reach 1236mT, the Hcb can reach 54.6kA/m, and the BHmax can reach 38.3kJ/m3。
Example 4:
the production process of the powder sintered alnico permanent magnetic alloy comprises the following steps:
step one, weighing materials: weighing 26% of Co, 14.5% of Ni, 3% of Cu, 9% of Al, 0.5% of Nb, 0.5% of Ti, 0.3% of B and 52% of Fe according to weight percentage;
step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow;
step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen so as to remove oxidized impurities;
step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three through a V-shaped or three-dimensional mixer to obtain alloy powder;
step five, pressing: pressing the alloy powder with a dry powder press to form a pressed product with a pressing density of 5.5-6.0 g/cm, wherein the die can be square, circular, annular or other shapes3；
Step six, sintering: placing the pressed product into a sintering box by adopting a vacuum sintering furnace, adopting 36-60-mesh corundum as a filler, ensuring that the sand purity Al2O3 is more than 98 percent and the sintering vacuum degree is required to be less than 10Pa, adopting 8-grade sintering in the sintering process, and then cooling and discharging to obtain a sintered product;
step seven, heat treatment: preheating a sintered product at 900 ℃ for 20 minutes, putting the preheated sintered product into a high-temperature furnace for solid solution at 1280 ℃ for 20 minutes, cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for 10-20 minutes when the temperature is reduced to 900 ℃, directly cooling the product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590-610 ℃, and the strength of a magnetic field is greater than 3000 Gs;
the five types of Al-Ni-Co are single-phase solid solution alpha phase at the temperature of more than 1200 ℃, alpha + gamma exists at the temperature of 1200-900 ℃, the gamma phase is a non-magnetic phase, the thermomagnetic treatment is carried out at the temperature of 900-600 ℃ to generate alpha → alpha 1 + alpha 2 amplitude modulation decomposition, and the key for obtaining high magnetic performance is to reduce the generation of the gamma phase. The conventional process adopts preheating at 900 ℃, solid solution at 1280 ℃, heat preservation for 12-18 minutes, air cooling, temperature control cooling in a magnetic field, and the magnetic field cooling time is 12-18 minutes. The conventional process still has a small amount of gamma phase generated in the range of 1200-900 ℃. The method adopts 900 ℃ preheating, 1280 ℃ solid solution, heat preservation for 12-18 minutes, air cooling for rapid 1200-900 ℃, then 590-610 ℃ isothermal thermomagnetic treatment for 10-20 minutes, and air cooling naturally, the process effectively reduces the precipitation of gamma phase, and simultaneously adopts 590-610 ℃ isothermal thermomagnetic treatment to avoid insufficient alpha → alpha 1 + alpha 2 decomposition caused by too rapid temperature reduction.
Step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours (first-stage tempering); cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours (secondary tempering); cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours (third-stage tempering), and then continuously cooling and discharging to obtain a finished product.
The 8-stage sintering comprises the following steps:
step a), heating to 500 ℃ from room temperature for 3 hours;
step b), preserving heat for 3 hours at 500 ℃;
step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours;
step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours;
step e), continuously heating to 900-1200 ℃, and then preserving heat for 3 hours;
step f), continuously heating to 1200-1360 ℃, and then preserving heat for 4 hours;
step g), keeping the temperature at 1360 ℃ for 6 hours;
step h), continuously raising the temperature to 1360-1370 ℃, and then preserving the temperature for 1 hour.
The invention reduces the copper content to reduce the coercive force, and compensates the coercive force by adding titaniumThe force is reduced, the content of cobalt and iron is increased, the remanence is improved, and meanwhile, the eutectic temperature of the alloy is reduced by adding the trace element boron, so that the growth of crystal grains is facilitated, and the sintering density is improved; the method adopts 8-level sintering, the temperature of the last sintering is raised to 1360-1370 ℃, then the temperature is kept for 0.5-1 hour, and the crystal grains are further grown by short-time temperature rise, and meanwhile, the product deformation caused by overhigh sintering temperature is avoided; the heat treatment of the invention adopts preheating at 900 ℃ and solid solution at 1280 ℃, then when the temperature is reduced to 900 ℃, the isothermal thermomagnetic treatment is carried out for a certain time, and then the air cooling is carried out directly to the normal temperature, the process effectively reduces the precipitation of the gamma phase, and simultaneously, the 590-610 ℃ isothermal thermomagnetic treatment is adopted to avoid the rapid temperature reduction to cause alpha → alpha 1 + alpha2Insufficient decomposition, thereby improving the magnetic performance; the magnetic performance Br of the finished product produced by the invention can reach 1241mT, Hcb can reach 53.5kA/m, BHmax can reach 38.2kJ/m3。
It should be noted that the above list is only one specific embodiment of the present invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible.
In general, all modifications that can be derived or suggested by those skilled in the art from the disclosure herein are intended to be included within the scope of the invention.
Claims (5)
1. The production process of the powder sintered alnico permanent magnetic alloy is characterized by comprising the following steps of: step one, weighing materials: weighing 24.5-26% of Co, 13.5-14.5% of Ni, 2-3% of Cu, 8-9% of Al, 0-0.5% of Nb, 0-0.5% of Ti, 0-0.3% of B and 46.2-52% of Fe according to weight percentage; step two, vacuum melting: melting Co and Al into a CoAl alloy in vacuum, melting Ti and Fe into a TiFe alloy in vacuum, crushing the CoAl alloy and the TiFe alloy to obtain crushed particles, and grinding the crushed particles into crushed powder by using airflow; step three, primary mixing: grinding Cu, Ni, Nb and B into powder and mixing to obtain mixed powder, and reducing the mixed powder for 2 hours at 550 ℃ by using hydrogen; step four, mixing again: mixing the crushed powder in the step two with the mixed powder in the step three to obtain alloy powder; step five, pressing: pressing and forming the alloy powder by using a dry powder press to obtain a pressed product; step six, sintering: sintering the pressed product in a vacuum sintering furnace for 8 grades, and then cooling and discharging to obtain a sintered product; the 8-stage sintering comprises the following steps: step a), heating to 500 ℃ from room temperature for 1-3 hours; step b), preserving heat for 2-3 hours at 500 ℃; step c), continuously heating to 500-800 ℃, and then preserving heat for 3 hours; step d), continuing to heat up to 800-900 ℃, and then preserving heat for 2 hours; step e), continuously heating to 900-1200 ℃, and then preserving heat for 2-3 hours; step f), continuously heating to 1200-1360 ℃, and then preserving heat for 2-4 hours; step g), preserving heat for 2-6 hours at 1360 ℃; step h), continuously heating to 1360-1370 ℃, and then preserving heat for 0.5-1 hour; step seven, heat treatment: preheating a sintered product for a period of time, then putting the preheated sintered product into a high-temperature furnace for solid solution for 20 minutes, wherein the solid solution temperature is 1280 ℃, then cooling the sintered product in an air cooling mode after discharging the sintered product, transferring the sintered product into isothermal thermomagnetic treatment for a period of time when the temperature is reduced to 900 ℃, and then directly cooling the sintered product to the normal temperature, wherein the temperature of an isothermal pipe in the isothermal thermomagnetic treatment is between 590 and 610 ℃, and the strength of a magnetic field is more than 3000 Gs; step eight, tempering: three-stage tempering is adopted, the temperature is raised to 630 ℃ along with the furnace, and the temperature is kept for 3 to 5 hours; cooling to 600 ℃ along with the furnace, and preserving heat for 5-7 hours; cooling to 570 ℃ along with the furnace, preserving heat for 7-10 hours, and then continuously cooling and discharging to obtain a finished product.
2. The process for producing powder sintered alnico permanent magnet alloy as claimed in claim 1, wherein the preheating temperature in the seventh step is 900 ℃.
3. The process for producing powder sintered alnico permanent magnet alloy as claimed in claim 1, wherein the period of time in the seventh step is 20 minutes.
4. The process of claim 1, wherein the certain time is 10-20 minutes.
5. The process of claim 1, wherein the pressed density is 5.5-6.0 g/cm3。
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